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Intel® 460GX Chipset Software Developer’s Manual 10-13
IFB Usage Considerations
10.5.7.1 BMIS1 - Bus Master IDE Status Register 1
(Primary: Bus Master IDE Base I/O Address + Offset 02h)
10.5.7.2 BMIS2 - Bus Master IDE Status Register 2
(Secondary: Bus Master IDE Base I/O Address + Offset 0Ah)
•
The Drive 0 DMA Capable bit shall be:
— Set to ‘1’ when the Drive 0 (Master) has been identified and configured for DMA
transfers (Ultra DMA, Multi Word DMA or Single Word DMA).
— Set to ‘0’ if Drive 0 is PIO only and/or not configured for DMA operation.
• The Drive 1 DMA Capable bit shall be:
— Set to ‘1’ when the Drive 1 (Slave) has been identified and configured for DMA transfers.
— Set to ‘0’ if Drive 1 is PIO only and/or not configured for DMA operation.
It is the responsibility of initialization software to ensure that these DMA capable bits are set so
that a PCI Bus Master IDE device driver can determine which drives have been configured for
DMA operation.
10.5.8 Settings Checklist
The following checklists can be used in determining drive modes. Refer to the “Determining a
Drive’s Transfer Rate Capabilities” and “IFB Timing Settings” sections for more information.
76 5 43210
Reserved Drive 1 DMA
Capable
(DMACAP1)
Drive 0 DMA
Capable
(DMACAP0)
Reserved IDE
Interrupt
Status
(IDEINTS)
IDE DMA
Error
Bus Master
IDE Active
(BMIDEA)
0: Drive is
PIO only.
1: Drive is
capable and
configured
for DMA
transfers.
0: Drive is
PIO only.
1: Drive is
capable and
configured
for DMA
transfers.
0: R/W/C
Software
writes 1’ to
clear.
0: R/W/C
Software
writes 1’ to
clear.
0: RO
Table 10-13. Drive Capabilities Checklist
Drive
Type
(ATA Fixed
Disk or
ATAPI)
Position
Best Ultra
DMA Mode
(Ultra DMA
Mode 0, 1,
2, or N/A)
Best DMA
Mode
(Single
Word 2,
Multi Word
1, 2, or N/A)
Best PIO
Mode (Fast
PIO Mode 2,
3, 4 or
Compatible)
IFB
Ultra
DMA
Mode
IFB
Mode
Non Ultra DMA
Supported?
Best DMA Mode
is {SW2, MW1,
MW2}
Fast PIO
Supported?
Best PIO Mode
>= Best DMA
Mode
Drive 0 Primary
Master
Drive 1 Primary
Slave
Drive 2 Secondary
Master
Drive 3 Secondary
Slave